NG Combi Boiler versus indirect tank and boiler setup

A combi boiler seems like a no brainer from the specs and what folks are telling me.

Right now we have an oil cast iron boiler that is 150kBTU. It has the domestic hot water and house baseboard heat feeding a 3350 sq foot house. The unit often short cycles and seems a bit oversized. A heat loss analysis is currently underway the right way to help determine actual needs.

Making the assumption that the ultimate choice of a unit is sized correctly for the house, people are telling us the unit will work perfectly for our needs. Our overall requirement is to run two showers and heat the house. If that means buy a bigger unit, no problem here. Naiven has some bigger units in our budget with 7.6 GPH, else Bosch or Triangle Tube 96kBTU Output at the smaller end. I am just the average homeowner trying to understand real-life experience from people that know more than me.

Has anyone installed a combi boiler in a regular suburban home with 4 bedrooms and 2.5 baths in New Jersey area like climate? If so, how do you like your unit or how did it work out?

Looking for real-world experience on this one. The job is half the price going this route.

Comments

I wanted to hear from the horses mouth. They said the system is designed for applications like ours. The installer just needs to install properly and run the numbers (delta T, run lengths, flow rates, heat loss, etc) to confirm the size is adequate.

The Naiven 180A, 210A and 240A units have the pump built in and a built in tank to hold pre-heated water so the unit does not have a cold pocket. They said to stick with that model for best results. They indicated that the experience would be the same as my boiler today. The only thing they gave further advice about is to make sure it is sized right for the house so that on a cold day we are not taking cold showers due to demands on the unit.

It was also said, very frankly, that anyone telling you different needs to go back to school. Times have changed in the last few years.

We are getting mixed opinions on combi boilers. Some swear by them in the past year or two, some say no way ever and recommend cast iron or Wells McClain units with indirect tanks.

The horses mouth didn't even give you the right piece of equipment for the job.. Those are tankless water heaters not a BOILER!!! You would be using their CH Series...

Like I've said in your previous thread. You need to figure out you GPM needs!! There is no way of going around it. The poster also failed to post that they FILL A WHIRLPOOL and multiple showers at once is a given..

If I was a betting man I'd say the CH240-ASME. In your previous thread you were looking at a Triangle Challenger that would only provide 3.5gpm which would not do the job...

We gave you all the math in the previous post.

GPM = Btu/hr / (Temp Rise x 500)

As long as the unit is sized appropriately it will do the job. For how long, that depends on the quality of the product purchased and most importantly the installation..

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

Make sure you have a heat loss program run on your house. Size the boiler for the heating load. If you want to run two showers at one time replace your shower heads with 1.5 GPM delta shower heads. They give plenty of hot water for showering. Triangle Tube has one model PE110 Prestige Excellence boiler with a built in indirect water heater. It delivers 180 GPH domestic hot water and it can run two showers with 1.5 GPM shower heads. They also have a Challenger Combi boiler that also makes domestic hot water all in one wall hung unit. They come in 85,000 - 105,000 - 125,000 BTU input models and they deliver 2 to 3 GPM on the domestic hot water side. If you think you need more domestic hot water use a prestige solo boiler with a smart 40 gallon indirect water heater or larger gallon model.

The Navien CH BOILERS work well. We've had no problems with them. As Chris pointed out, the models that the "horses mouth" gave you are water heaters, not boilers. The boilers also do not have a storage tank built in. But, the controls work very well in switching from space heating to domestic.

There is one caveat with these units: the on board pump can only deliver 5 gpm. for space heating. With high temp baseboard like you have, that translates to 50k btu'sat a 20* Delta T, 170* average water temp. It doesn't matter that the burner is 199k, the pump is only going to move enough water to deliver 50k btu's at the above numbers. The pump is sized for domestic heating and at 5 gpm, 77* Delta T, you get 192.5k btu's. The only way to get more btu's for space heating is to widen the Delta T which is only possible if your base board is over sized or you add more emitters which would allow for lower water temps. and a wider Delta T.

Take a look at ther optional manifold, I've seen 110,000 btu + jobs, 180 degree installs working fine. Actually they can put out more Btus because they only modulate down at about 6 degrees from setpoint, staying on longer than a on/off 20 DT boiler.

I sell and recommend a lot of standard cast iron boilers... A good cast iron 85% gas boiler wont be replaced for a long time... High efficiency doesn't always add up, especially in smaller homes with smaller loads...

A 1400 sq ft home with decent insulation {say a heat loss of 27KBTU} would do much better with a small Weil McLain boiler installed for 25% the price of a mod con and will last twice as long makes a lot more sense than a Mod con....

If they are paying $1400 a year for heat, you will have to save them around 40% over a standard boiler, and with a properly sized WM Gold with an outdoor reset and delta t circulator, your not going to get a mod con to outlast or get better than 15% savings {max}... Now with larger properties and much heavier heat losses, yes, it will save the customer money in the long run because they are spending $3000+ a year for fuel, but even then it gets sketchy with how ong these mod cons are going to last, I have cast iron wet base boilers that have been running for 25 years {I installed} and look to have a decade left in them, I have yet to see a mod con that looks like it is going to last 35 years without major service....

Sorry, I just don't see how any company should be shut out for recommending standard equipment, I install 50+ mod cons a year {not counting DHW tankless units} but last year I still sold over 100 cast iron boilers....

But anyway, a message to the OP... When I go to a sales call and the customer says "I wan't this boiler", I have yet to see them make a better decision on equipment than me... I had a customer insist on me installing an Trinity unit, I recommended using the equipment I normally install but he was adamant about the NTI brand and said he did his research and thats what he wanted.. In this situation I tell the customer to buy the unit online {which he was happy to do} and I told him, I am in no way responsible for this unit ,I am simply installing it in your home, and I will do so in accordance with local codes and the manufacturers instructions... We came to an agreement on price and the job was done, I have to admit it looked very good, my guys painted the back board flat black, and even painted the covers of the taco zone controls grey to match the trinity, I talked the customer into using ss circualtors and no iron or steel in the install all ss, brass, copper, pex, with a filter, long story short it was an impressive install...

About 3 months goes by, and the board cooks, OK we change t, he pays for 3 hours labor and waits 11 days for the board, 4 months later, another board similar costs again, I would say about 2 months after than another board, this time I personally call NTI, they send a "new updated" board, about 6 months goes by and the HE is leaking!!! This entire time he is dealing with NTI, so a couple days after the leak is found, I get a call from the home owner, and we end up installing a GB142, hasnt had 1 problem, and he was man enough to admit, he should have listened to me...

So the moral of the story is, get some one out there that you trust, and let them tell you what to install... The TT is a good choice for equipment, but let the tech tell you what he thinks.... you will be happier in the end... If money is the issue, than go with a real nice standard boiler {buderus with a good control} and dont worry about a thing for 30 years...

ONe more thing, I wouldn't go combi for what you are looking to accomplish, get an indirect or an od tankless...

According to the installation and user manual, the Navien CH 240 ASME boiler switches off the baseboard heat when Domestic Hot water is called for. There is also an on-board tank and pump to the unit to mitigate the cold sandwich effect I have been hearing about. Also, the diagram has three zone circulation pumps in the install guide, just like my home has.

Given this separation between Domestic Hot water calls and full heating, it sounds like this unit could be a nice practical option for a standard 4 bedroom 2.5 bath home in the suburbs. This also appears to be the only combi unit on the market of this size to make this feasible.

Is this unit different from the rest out there? Could this be a new option not commonly used yet for folks?

The flow rate is 8.4 GPM at a 45 degree rise and 4.9 GPM at a 77 degree rise. For the two shower requirement, it seems that 4.9 GPM would suffice, and then some for us folks in New Jersey. My flows fall below this when running a tub and shower at my bathrooms now. Roughly around 2 GPM from the shower currently when doing the bucket test. The largest tub faucet runs around almost 3 to almost 4 gpm roughly.

I guess this means that when folks are taking showers, the house gets a big colder though. Would we have to just make sure the wife does not take a 12 hour shower?

Anyone have any practical experience with this particular unit to advise?

We would feel better to hear about someone that is successfully using this combi unit in a typical suburban home. It is a 240,000 BTU unit after all. That is pretty substantial.

All modern systems have Hot Water priority for the showers and fixtures. Triangle Tube Prestige has a domestic tank that stores a little bit of water to handle that sandwich effect and instant demand lag.

Of cold water slug is what has cooled down in the piping system. No way around that unless you have a hot water recirculation loop.

Glad to hear you took my advice and did the bucket test. Based on what you posted you need to size for 6 gallons per minute delivery. The unit is only going to fire at full fire when you need a full load. So when only one shower is going it will fire to the needed btu/hr for that demand.

6 gpm x (70 x 500 ) = 210,000 Btu/hr

The CH-210-ASME is the correct choice if you decide to install a Navien unit.

As for a referral. Think it would be best if you ask the contractors bidding on the job provide actual installation referrals then asking one of us. Any of us could tell you it's better then sliced bread but unfortunately no matter the equipment, it is only going to perform based on the mercy of the guy actually installing it.

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

We have a contractor steering us to the Triangle Tube Trimax Excellence Series instead of the Navien. But that unit is about $2000 to $3000 more. They both seem to do the same thing and have very similar performance specifications from what I am reading so far. The efficiency on the Triangle Tube is rated higher though, 95% compared to 91%. That is the only thing I can tell.

Is there a big justification to the $3000 difference besides the efficiency number?

Triangle tube is a boiler first that makes hot water, the navien is a water heater that can do a little heat. Triangle has a good reputation, they also have excellent customer service and troubleshooting is a bit simpler typically because of a bit more room in the unit.

If it was my home, I would do just what you are doing and do my homework. It is important that you are aware of what the boiler is capable of in terms of hot water. Do you have a soaking tub or jacuzzi tub? If so the boiler will struggle if it can keep up at all. Though I may be a little out of line with this since I am basing it off the original prestige excellence numbers.

Well, I got my first quote last night on the Navien and Triangle Tube units. They pushed the NJ State rebate program which offers a $4k rebate.

The contractor said the navien is a more time consuming install, even though the unit is $2k cheaper, he said it would only be slightly less expensive than the Triangle Tube Trimax Excellence Series. I was curious and asked why but he indicated he would not discuss the details as he is not a line item by line item type of guy. It seems like the Navien combi and this unit would be a very similar installation, but I only read the installation guides as my point of reference so far.

All in, the quotes came down to recommendations for the Navien CH-210 and Triangle Tube Trimax Excellence Series units. The work involved removal of the old boiler, installation of the new boiler, three new recirc pumps, two new zone valves, a pressure tank and new backflow preventers. Also, they would pick up my small empty 4 year old 200 gallon oil tank away to the scrap yard for me. In addition, to qualify for the state rebates, the contractor has to seal up the house. The house is very well along that path already, so they are only planning to go after low hanging fruit with spray foam in the attic and niche areas with one person while the guys install the unit. Like I said, the house is already pretty well sealed compared to its prior state, poor to upper-end average now.

All together I was expecting a quote for around $6500 but got a quote for a little more than double that with a $4k rebate off. Seems like the contractor is trying to have a boondoggle at my expense. $7k profit for two days of work? Am I way off on my thinking? I was getting quotes for much less without rebates and state assistance. Without the insulation job, I was thinking it could come in possibly a bit lower as well.

Am I totally off base with my thinking? Looking for a sanity check here.

Is that talking pricing is not allowed. Don't expect an answer to your question as it pertains to anything about price.

The Excellence has a 14 gallon indirect built into the boiler. Once you dump that tank the recovery rate is no different then the Challenger. You need to be able to deliver 6gpm at peak demand.

The PTE110 in a 10 minute peak flow will provide 55 gallons or 5.5gpm as shown in the literature but that's based on the installer adding a mixing valve to the DHW out, a 108 degree setpoint and 50 degree incoming cold water. Are you going to be ok with 108 degree hot water temp? If no mixing valve this is going to be reality if your making 120 degree DHW.

110,000/ (70 x 500) = 3.14gpm x 10 = 31 + 14 = 45 gallons in the first 10 minutes or 4.5gpm. Once that 12 gallon tank is done your going to be running on a 3gpm capable delivery. Do we have teenage girls that shower longer then 10 minutes? Will 2 showers be running simultaneously for longer then 10 minutes?

Just more questions..

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

The internet hurts homeowners and contractors when it comes to the pricing information available. I know it looks like this guy is making $7000 but that is simply not the case...

Put it this way, IF you can find me someone to do what you want done for the prices you listed, I will give them a job today, heck Ill even throw in a 10% bonus on top of your pricing...

If they install that equipment for that price correctly and then give support {that most likely be needed} and service for the warranty period, they will be out of business after 3 jobs...

Here's the thing, I know we can't talk money on this sight and it is a good rule {that I reluctantly break all the time}...

So I am going to go off the grid here a little, because the regular joe homeowner thinks we are making so much money off of these jobs with out looking at the entire picture....

So I am going to just give you a quick idea of the math I deal with on every job looks like...

FIRST LABOR- My techs cost me around $45 per hour after tax matching, wages, overtime, health coverage, vacation and sick time average... and your install will take 2.5 days 2 techs {if not more between sending someone to do your heatloss, making parts lists, removing old equipment, ordering your equipment, billing, driving ect} and if we never have to go back because "your upstairs bathroom used to be warmer or you smell a funny odor or it made a different noise" ect, you would be surprised how many new installs get these non sense call backs that we have to pay for...

so in labor, your job is costing me $1800 {thats 2 techs 2.5 days at $45 per hour}... Thats if we are not in overtime that week and its February so I can count on time and a half for these months...

NEXT EQUIPMENT Your equipment prices are off. {I don't install Navian, but I am familiar with their costs and associated costs} and with out the spray foam {I wouldn't get involved in that at all, you would need to call an insulation company to take care of that}, you are low.. But I will say contractors pay more than companies like pex supply sells the equipment for, and you were nice enough to add 15% profit but I pay 7% tax so now you are down to 8% profit which is insulting, I won't make that phone call to order the equipment for 8%, the paperwork and accounting involved in accounts receivable and payable will eat that 8% up faster than you think.. in short, what I pay my accountants and book keepers will make short work of an 8% mark up on parts...

So now since my techs wont walk to your house- TRANSPORTATION --- I pay $35,000 for a service truck that lasts 4 years {if I am VERY lucky} {after 4 years they have 250K+ miles on them and are worthless by then}. My business plan needs the trucks to last that long so I do my best with it... In that 4 years I will put 4 sets of tires on them at $1000 per set,and do about $15,000 of service total {oil changes, alignments, alternators, ect} , I will pay $7000 in taxes on it, and here is the big one I will spend almost $90,000 in fuel in them 4 years with per truck!!! {do the math 250,000 miles dived by 11 mpg, X $3.88 per gallon}. so that truck costs me $150K for them 4 years which is around $40K per year, and it works on average 250 days per year that is about $175 per day so you will need 2.5 days of that puts your jobs vehicle cost alone just under $450....

Next lets talk about my office, it employs secretaries, I pay taxes on the building and pay the mortgage, I pay for internet access, and phone lines, and advertising, and heat and air conditing, and electricity, and landscaping, and upkeep, and the list seems to never end.... Its harder to put a number on this since I have equity in the building but not all companies own their office and garages... But lets call it $300 per job...

Next is insurance, registration, permit/inspection fees, licence/training costs, and advertising {truck lettering, signs, adds, ect} this adds another $700 to every single job...

Im not even going to add in tools consumables, stuff like solder that costs $35 a roll now...

So now we can talk about my profit, yay... I would make about $800 total on your job which I will pay 30% of to uncle Sam leaving me the "company owner" with about $550... And If I do the work instead of sending 2 payroll techs I will only just about double that... All my experience and investments come down to a measly $220 per day!!!

So the prices are not as bad as you think, I don't know what your contractors situation is but that is a fast breakdown of what your install would cost me...

I apologize for talking about money, but that is why we are all here, to save it, make it, or spend it.... Its all about money...

So my advice to the OP, don't get too hung up on figuring out the contractors profits, it will make you crazy and resentful, concentrate more on getting a good heating system that will work for many years and be reliable and efficient...

I honestly don't like combi units and in smaller heat losses don't think Mod Cons make a lot of financial sense.... Do yourself a favor and get 3 quotes, from 3 contractors, spend some time talking to them and then make your decision... Either that or go on craigslist and find someone that will work for $100 a day that knows how to install boilers, but most likely he is going just going to take your money and steal your chainsaw {I had a customer pay a guy $4000 cash to install a boiler, and the day they dropped the boiler off he got paid and on his way out "to get the rest of the parts" stole his chainsaw and never returned}...

You will be much happier with the job if you get someone qualified to do it, and that costs money...

Good luck, I hope you find someone that you can work with and get a nice system out of it, what part of the country are you in did you try the contractor finder?

Hey, these are big number for a homeowner to digest too guys. This last quote was not broken out in any way, so it naturally leaves someone wondering.

At the end of the day I want a fair price. I don't mind someone making a living. I don't mind paying for value and building a long-term relationship. I don't want to get taken for a ride either. I can see by this there is more to factor in. I am guessing that I would probably factor in a rough $80-100 /hr rate to account for the typical business overhead costs and factor in a 33% markup to the online numbers found?

The quotes I have received are all over the place, even for the same things.

So from the looks of it, an $8k quote is not that far off at the end of the day. That is good to know.

Now, this is the part that makes me wonder. In this instance, the contractor will also get paid an additional $6k from the state in rebates, in essence making this a $13,000 - $14,000 job. What benefit does a homeowner get here from going with the state program? I am looking at paying the same price either way.

Since you still have a functioning system, try talking with your contractor of choice and see if he will cut you a break by doing it in the spring (shoulder heating and cooling season). Allot of companies are slow at that time of year and appreciate "busy" work for their techs. It never hurts to ask.

did you ever get a heatloss number, I looked through the posts fast and couldn't find a number, a 3300+ sq ft house can have a heat loss from 60K- to 125k+ depending on layout, location, insulation ect?

I find when I go to retro jobs, I look at a few things

first is the customers budget, I don't want to bring up a system you can't afford because then you will think I'm not giving you the best...

Next is your existing system, is the baseboard over sized to allow for lower boiler temps, is it zoned off at every turn making a mod/con troublesome, can I use the chimney or can I sidewall or roof vent, what are the fuel options, ect....

So when we give you advice on which direction to go we only have the info you share with us.. From what I have read from you so far, to me it seems like you want to get the most for your money and end up with an efficient low maint. system that will last a long time...

I will say this, I have been in this business a long time, I have seen systems and companies come and go, and I recommend to my customers based on what I would do in their situation not what makes me the most profit or is easiest and fastest to finish...

For longevity and low maint. I like cast iron wet base boilers, I install mod cons and have them in some of my properties but when it comes down to it, its a trade off, and if you are up for the higher initial costs and lower reliability and longevity for a 10%+ eff. boost then go for it, lots of people do...

BUT for the most part in a home with a low heatloss {I say sub 70-100K}, I tend to recommend cast iron gas boilers... {I install against my recommendations lots of mod con in small houses, most of the time because there is no room for a boiler or the customer is a techy which is great, and I want to give them what they want, but I have also saved people money by explaining the ins and outs in detail and letting them make a more informed decision.

So long story short for you.. If I showed up at your door...

I would say... For heat ----- If your heatloss is lower than 60K BTU go with a weil mclain CGi series boiler that fits your loss they go all the way down under to 40K {which you are probably way above}.

If your heatloss is between 60 and 100K go with a Buderus GA124 series, this is where I think you will fall...

now, Im not sure how much baseboard you have or what kind, but have your heating contractor add it up and come up with the lowest operating temp for your design day, this may be around 160*, and have your heating contractor install delta T circulators {bumble bees are nice} and an aquastat with an ODR sensor {honeywell, hydrostat, even $logamatic$ if you want to get fancy, but there is no need the hydrostat works great}, also make sure they pipe in intake air for your combustion and direct vent the boiler.... These few things will get you the most out of that boiler and almost' level the playing field with a mod/con...

Next is your DHW, I like tankless water heaters, I have been installing Rinnai units for a long time {since they were released in the US, I think I bought the first one, lol} and they are reliable, I have them in one of my rental homes that are 10 years old with well water and I have never even descaled them, they work great and save energy.... Now some people will say tanklesses don't last 5 years, but the fact is the warranty is for 12, you get a rebate for installing them, and I have never replaced one yet, I have fixed a few, but very little...

I would have your contractor figure out your needs {or do it yourself} figure out your temp rise and usage and go with the Rinnai Ultra that fits, either the ru80 or ru98...

You should be able to get that all done for a fair price and it will last you a long time, just get the rite contractor out there....

Thank you for understanding my post about money, I was nervous you would take it the wrong way and think I was trying to single you out, it was in general, I see it all the time, I go to a customers house to price a tankless, and they go on amazon and say you want $2200 for it, but I can buy it "online" for $850 and you said it will only take 4 hours to install so you must make over $350 per hour!!! And of course they dont think about the venting the $60 hole saw Im going to burn out drilling through their stucco, the piping, the insurance ect... So I thank you for being open minded and understanding where I was trying to get....

Now if we could just get you to see a combi may not be your best choice, lol... I honestly only like the excellence combi, but it is not for everyone, it doesnt make a ton of hot water yet has a high btu output, so the heat side is good for a large home but most large homes have HUGE DHW needs... the 60 in a combi would probably be better...

PS, I know a few guys on here will think an indirect is the way to go for DHW and they are also nice {some of them, I like the TT Smarts}, and that is what makes this board good, you get a bunch of different outlooks... But I like tankless units for many reasons, first is efficiency, you are getting 95% vs firing your boiler at 85%, you are only heating the water to the temp you need {no more heat to 140 and cool it down with the tempering valve, you paid to heat it just to cool it down, makes no sense}, you can never run out of hot water, when you are not using it it is not using fuel {your tank is making hot water 24-7-365-8}, you can shut down your boiler as soon as you dont need it {with an indirect you run your boiler year round and sometimes need to maintain a higher limit}, ect...

Now with that said I don't want to be one sided, they are not perfect, if you turn on the hot water and then off, you will get a small bit of cold water in between{sandwich effect}, the hot water will take around 2-4 seconds longer to get to your further faucets, and it needs to be vented separately. The cost is about the same as an indirect {after circulator and priority control}, but you also get the rebates... I would say they will last as long as a smart tank since i have changed a few faulty smarts and never had to change a complete rinnai unit, the smart tanks are supposed to be good for 20 years and Im sure they will last that, but I think the Rinnai will also...

Isn't the Navien CH series a mod con? I see it is definitely a condensing boiler for sure. They have an outdoor sensor as a $125 option, which I would definitely want. Does that mean it modulates as well condenses and fits that description?

An outdoor sensor can be connected to Navien's Condensing Comi Water Heater. With this device the unit can automatically regulate the heating temperature according to changes in the temperature outdoors, allowing for precise indoor heat regardless of what the weather is doing outside."

Based on the inputs from Chris above, the Triangle Tube Trimax Excellence will not meet our Domestic Hot water needs for two showers at the same time, although the build quality looks really nice. But the build quality on the Navien ASME seems to looks pretty good too.

The heat loss is estimated to be somewhere in the range of 80,000 to 90,000. Significant upgrades to the house were made to turn it from a poorly insulated house to an average or slightly above average home now.

Existing system has 3 pumps. One that is 1/25 hp servicing the closest downstairs loops. The longer loops are running traditional 1/12 hp pumps. The pumps are running two loops each, as there are two sets of bleeder valves diverting from the pumps. They run very well and appear to work well for our needs.

The current boiler system is a around a decade old and around 150k unit running oil. It is an 87% capable boiler with an energy sticker on the size rating it at 83%. It runs in brief time frames even on the coldest days of the year. Assuming that means it is too big now. Also has hot water from it now as well. It runs very well, fully meets our hot water needs and is well balanced. The only complaint is the massive amount of oil this thing is burning.

The runs are 3/4 with about half being the nicer cast iron baseboards and the other half being the traditional copper fin type. The system is nicely balanced.

There are 4 new programmable thermostats around the house. There are three zone control valves.

A chimney flue is used by the oil boiler now, but it is not lined. It is a standard 9x13 size. The boiler location is in an unfinished basement against and outside wall ideal for direct venting.

A 1" natural gas line feeds the house. A main 1.25" line is at the location of the current boiler. There are two additional taps available in 1.2" and 3/4" sizes now. This was by plan put in for this oil to gas conversion.

The oil tank is a relatively new 200 gallon tank that sits above ground just outside in the side yard. I have no idea why such a small tank was put in, but we are not complaining.

The reason the combi looks so attractive is that we can get the high efficiency unit we want for the low cast-iron boiler and separate water heater price. It appears to minimize the parts needed and also eliminates the need for a chimney liner.

From what we can tell, the total cost of parts between the combi option and the separate 50 gallon water heater and 85% boiler option are in the same ball park. It seems like the labor between installing the two types of boilers would not be drastically different, since the time frames given for installing both these options from contractors is estimated at a 1.5 day effort for the same amount of people. So to us for the same amount of money, we could have a higher end setup for a lower end cost, hence why it is so appealing.

Stretching our dollar, as with anyone, is a major factor in our decision process.

I have a better idea about your situation now, I have to say, changing good equipment ffor the sake of saving money on efficiency is a HARD sell {or at least should be}, you see when your equipment is in need of change because it has lived its life moving up to high eff. makes sense, but in your case you have a working boiler that probably hasn't even seen a third of its life yet.. So now you have to figure in how long that unit woud have lasted in your savings.... Its not going to add up....

And what makes it worse is you are comfortable with the system...

What is the make and model of your existing boiler...

How about this...

Install a conversion burner and an outdoor reset control on your existing boiler? get the remaining 20 years she has in her out, then go with something new....

You can get a carlin ez gas thrown in and you will have a nice gas boiler.. I would still throw a natural gas condensing rinnai tankless water heater up {as you can see I don't believe in heating up your boiler year round and in the summer at all}...

As far as the existing boiler being over sized, when the carlin is installed you can have your installer adjust it to your heat load and install it with a hydrostat aquastat that is odr capable...

This will save you on the oil get the life out of your existing unit and not be a huge expense...

I have down fired oil to gas boilers for shorter heat losses with good results... carlin ez with a #1 drilled orifice is 100K btu, you will want to start there that is about 85k out...

We had folks come out for gas conversions originally. The manufacturer said it wont work for gas so contractors are reluctant to touch it. They showed me in the user manual for the unit where it clearly states not to convert it. I forget the brand off hand. It is a big blue unit.

For the ones that would actually agreed to take it on, the price of converting the original was only $1000 less that replacing it with a new 83% with 50 gallon hot water heater. So then this whole convoluted process began.

Plus, they said that keeping that thing heated 24 hours a day for 365 days a year for hot water was a complete waste and it was too large for the house at this point anyway. Plus the oil service guy already said is tuned the unit to run lower with a smaller nozzle to save fuel for us last year.

We considered what you are proposing as well with separating the hot water off the big unit as well but only with 50 gallon traditional water heater for budget reasons.

The gas conversion unit was roughly $700-$1000 in parts in total, a $500 chimney liner, then a $800 water heater and about $300 in piping, valves venting and other miscellaneous parts. That is about $3k in parts. We got a quote for $4700 for a brand new 83% gas boiler and water heater, and everything would be new and got us thinking. The quote for just the gas conversion alone was $2900.

In doing further research, it appears the Navien will cost around $4k in parts for my setup. My pumps are just rebuilt and one is fairly new, so not planning on throwing them out. Reuse on them was recommended by all contractors so far. Thermostats are all new as well. Also good zone control valves.

The rough cut we came up with in parts for the 83% option and 50 gallon hot water heater was around $3500 for what was proposed.

When we ran the numbers for all the labor and parts it worked out to not much under the same cost in parts for the Navien combi unit but we would end up with a pretty efficient condensing and modulating unit. Plus I can mail in for some state rebates going that route as well, I believe $900.

Now, I am just talking part prices off one online supply house with no markups to keep it apples to apples for consistency when analyzing this. Labor estimates and people is also the same time frame and people estimated for these options as well.

First, the contractor gets the rebate and not the owner???? I find that kind of hard to believe. Also, 4K, wow, our rebate here in Seattle is 350.00 for high efficiency boiler. It can go to 1200 if a non storage type hw generator is used, no storage capacity of any amount to speak of allowed. Just a foot note.

Re: the type of boiler/heater. We are big fans of TT Prestige or Lochinvar WHN boiler. Same basic heat exchanger design. Good reliable pieces of equipment. Have installed around 60 of them with indirects most the time. The problem we find with combi units ie Navien, Takagi etc etc is they are just sooooo plugged full of sensors, flow sensors, electrical components that they are bound to fail, The 10 yr cost of ownership I feel will broach the cost difference of boiler vs combi unit. Just my take. Good luck, Tim

One is a standard rebate program.As far as I was reading the submittal form, it appears either the homeowner or the contractor can submit a rebate form for an either $300 or $900 rebate depending on the efficiency and types of systems installed. I think the homeowner can also submit with the contractor's information and proof of install on that option and get the check. I could be wrong though. There are not as many hoops to jump through for this one.

The other rebate program is a tiered program with a whole house audit and energy analysis. That involves sealing things up better and decreasing the heat lost from the house to a target number. I believe for 10% better it is a $2k, 20% better is $4k and 25% better is $4k. They guys out said they basically have a guy go through the attic, and other areas with a spray foam insulation mixer on his back and seal up everything., or at least in my case whereas most of the leg work was already done in to bring the house up to par with widows and insulation. In this program, the contractor gets the money and has to get certified into the program. On top of that, a state inspector validates the before and after results hit the goal.

That is great you have experience with these units. Seems like you have done some work with the Navien CH-210 and 240's before.

How have these units been? Are they more difficult to install than other boilers?

I also, had concerns like you mentioned on this thing's reliability. So, I searched around until I found a couple of people that had installed a number of these.

From the two contractors I have just recently spoken to, they were very honest. They said in the 2008 to 2010 time frame, they had some growing pains but Navien always replaced the parts and compensated them a bit. Since then, they indicated that they only sell the ASME commercial version and worked out the kinks. Since 2012, they have been rock solid. One contractor has done about 40 installs and the other has done around 20, but they don't service my area unfortunately. They said they like Triange Tube a bit better since they seem to come with more stuff bundled together in a kit and have a floor mount option rather than a wall mount setup. But that was their only complaints from both of them over the past couple of years. They both said the Challenger and higher end combi would not meet my needs for hot water in our home, just like you all were telling us. Interestingly, they also said they had more problems with Well McClain indirect tanks going bad than with the newer Navien units, which was surprising.

I am in a very similar situation and found the information in this thread very informative. I recently purchased a 1750 sf 1950s raised ranch that's currently being heated by an oil American Standard boiler that's also supplying my DHW; by best estimate, it is the original boiler. We have recessed cast iron rads on the main living floor, with cast iron baseboards in the basement. Considering oil prices being what they are, I very much need to replace a system that's currently operating at around 60% efficiency..and that's probably being generous.

I have been shopping around for the best replacement setup for our needs, which I should outline now; we're a young couple that have intentions of having children and possibly expanding the home down the line. The 6 gallon tank inside our boiler is barely supplying enough hot water (shocker) to our 2.5 baths. We have not even attempted heavy demand; 2.5 baths + dishwasher + clothes washer would be impossible to run within a few hours of one another. Being that it's juts the 2 of us now and we're already running out of water after consecutive showers, we're hoping to take care of this in the coming month. The original, single-paned slider windows are still throughout the house, which will also be replaced eventually, but not before the boiler installation. Insulation throughout the house is average at best. The existing boiler is tied into a fireplace chimney in our basement that keeps us from utilizing the area in front of the fireplace (the oil boiler sounds like a jet when it kicks on), so we are also intending on installing the new boiler elsewhere in the basement, in all likelihood direct vented.

What helps us is that I am an architect and pretty handy, so my intentions were to replace the boiler myself to help with my budget. To pay for college, I was a plumber's apprentice for a few summers and winters, so I am not really intimidated by the job, but rather making the right decision for my home for the next 30 years.

We've spec'd Navien combis on a few buildings we've done in some urban multi-family buildings in northeast NJ which have given us nothing but trouble, but I believe it has a lot to do with shoddy installation. Our plumbers from that job has complained about the trouble it's been to have Navien reps to take care of their issues and overall below average customer service. With that being said, I am still open to their product, just with a grain of salt. We have a bit of a hard water issue here, so I have been reconsidering my initial desire to use a combi system and almost have totally eliminated anything but a stainless steel heater.

I have generated a manual-J for the house that is giving me around 67k BTU heat loss, so I am thinking of a minimum of 80k BTU for a replacement. I was planning on a blower-door test, but I already know the house won't fair all that well. My quandary is deciding what brand I should go with; should I go with a combi unit? The TriangleTube Challenger unit is intriguing, but I've also been interested in others. Should I go with an indirect DHW tank?

I'm am curious how @HomeOwner1 has made out thus far and I appreciate any assistance in advance.

Assuming the Manual J had good inputs, you can size the boiler for that load and then size an indirect for the expected DHW demand. 80k firing rate on a fire-tube mod/con should be just about perfect. When you add on to the house, just plan for enough envelope improvements to cover the increase in square footage.

I am pretty confident the model built was accurate, I suppose I'm just second guessing myself. There's a difference between running the calcs for a customer and running it for myself :-D

As I see it, this is a vote for a mod/con boiler w/ indirect hot water.

I should point out that I was not intending to hijack this thread, just kinda piggyback on it. I am genuinely interested in how the results have turned out for the OP or if a boiler has been selected/installed. If anyone feels like I might have overstepped my bounds, please put me in my place

We are very happy with our Navien. Trouble free so far. We just needed to pay attention on how to install it correctly. It is a bit different. Primary loop, sizing, monoflow T's, pumps on supply not return so reverse the mounts on your existing pumps, no pressure reg needed on makeup since built in, etc...

Chris on this forum was helpful for figuring out hot water flows for gpm and that this unit met our technical needs. So the hot water dictated our BTU's required, not the heating load side.

This particular unit modulates all the way down to 17kbtu if I remember correctly, so it can compensate a bit. I am assuming that probably gives some tolerances on sizing on modulating condensing boilers installs, but best to ask the experts on that one.

We looked at the Challenger, for around the exact same price, but you get less for the money and the flow rates advertised are a bit deceptive (107 degrees for first 50 gallons or so whereas the Navien handles our 3 full baths with no issue). The higher end Triangle Tube was also in the same ball park for the build quality was but cost twice as much as the Navien and did not provide the same hot water or heating output necessary to support our bathrooms and hot water needs.

We have a pretty big, but mostly well insulated home now. Our heat loss probably falls around 85 kbtu based on calculations.

I was originally concerned about the lag between the heater heating up hot water and getting to the showers. The unit is pretty fast to heat up though, which was surprising. Sure you will wait a few more seconds that having the water already heated up, but the family has not noticed any changes, so obviously is acceptable, maybe an extra 15 seconds I would guess to ramp up heating. We set our hot water temp to 130 degrees and seems to be the right setting for us. Heat loop temp can be adjusted for max temp as well.

For some reason, I could not find many installers out there that either knew anything about the unit or was willing to work on them. Almost everyone of them wanted to install a Cast Iron boiler or a much more expensive Weil Mclain with Indirect. Nobody had consistent answers or advice for our home, and just about everyone of the installers never had done a combi installation ever before. Only the guys originally from Europe knew there stuff it seemed.

For the money, this unit made a lot of sense to us given the reduction in parts to install. We ran the exhaust up to the roof, which we are glad we did as well given the wet vapor cloud the condensing units apparently seem to all put out when observing other units out there. The hardest part was all the plumbing rework. Good luck.

Also, the unit does not come with the Outdoor Rest Sensor in the box. Make sure you buy one. Call Navien support for their Curve formula so you can input into the control unit, it is not in the manual for some strange reason.

I'm in the process of converting my heating and hot water from oil to gas. One of the licensed plumbers mentioned that the Navien Combo unit does not work with generator due to the generators electric output fluctuationg which keeps reseting the boiler. He said he confirmed this with the manufacturer.

Sounds like a pretty bad generator if it cannot maintain 60 hertz. Voltages can vary.

Put a good server UPS with filter on anything electronic you care about in that house if that is the case no matter what you install. That would solve the issue for anything connected to it for a low cost. They take AC power goes to DC battery, and puts back to really clean AC on the good ones. That would solve the problem and keep anything protected connected to it, if rated for the usage.

I'm going through the same thing. The rebate program in MA is upto $3500 plus $450 for the water heater too if the new units are 90% or more efficient and installed by Oct 1.

When Mass Save Program's analysis was done, it found that my 30 year old Teledyne Laars Series J boiler is not that efficient any longer. Probably running 70%. It's a natural gas system.

The problem that I'm running into, is that even with a $4,000 rebate, the cost to me is over $10,000 to put in a high efficiency on-demand system like the Bosch GreenStar Combi 151. If I save 30% of my annual $2000 fuel costs, I save approx $600 per year. So I figure 16 years+ to return my $10,000 investment. But in order to keep the warranty requirements met, I need an annual maintenance that costs about $360 per year. Now my return on $10,000 will take 33 years to pay for itself. I'll probably move or be dead by then. So my question is:

How does a home owner justify these purchases? My old boiler is 31 years old, but I'm thinking maybe I just want t replace it with a standard boiler and separate water heater. I don't know how much that costs yet, but

Water heaters last about 6 years here and a 40 gallon unit is about $500 to replace (last one was anyway). The current one is only 2 years old.

I've read the posts here and find them impressive with all the straight talk and info, but I'll have less than 6 weeks to get one installed to take advantage of the rebate program. I'm now thinking it isn't worth the rebate fuss.

With trying to justify fuel savings by AFUE. AFUE does not take into account that a modulating condensing boiler only fires to its full btu/hr output 2% of the heating season if at all.

Its not a fixed firing rate as your current boiler is. For example, come that first day in Oct or Nov when you flip on the heat your current boiler fires to its full btu/hr output, a condensing boiler will more then likely only fire to its minimum out put. So, Oct, Nov, Most of Dec, Mar there is no way on earth you'd see it fire to more then 50% of its output unless the temp outside dropped.

Dependent on the install, I'd say your more likley to cut that fuel bill in half if not more. You also cannot look at dollars you have to look at Therms consumed. Price of gas changes year to year right..

"The bitter taste of a poor installation remains much longer than the sweet taste of the lowest price."

Even if I save 1000/year in fuel costs, the annual maintenance drops that to $640. That still means 15 years before I break even. Wouldn't it be more economical to either replace my current boiler with another modutherm cast iron boiler or possibly get this one tuned up? I don't know if there is such a thing as a tune up for a gas boiler, but if there is, that makes more sense to me. 16 years payback is no incentive at all.

I get the sense that there is a long period payback even with the rebates. How do people justify going high tech?

I look at the warranties and see a range of 1 year up to 5 years on parts, up to 12 years on heat exchangers. The much higher complexity of multiple electronic components makes then inherently less reliable meaning more service calls. Add to that the condensate needing special treatment before going into the drain, or the call for water softeners to extend the life of the unit, plus the annual service visits seems like I trade gas savings for increased cost of ownership.

Add to that the need to make a decision in the next few weeks seems like I should forgo the rebate program and go with a standard boiler.

Right there in Mass (East Freetown) is a company that makes equipoment well suited to your concerns and needs . HTP (heat transfer products) makes a unit named Phoenix . It is in effect a water heater that is constructed of materials that are very hearty , cupro nickel heat exchanger , stainless . This unit offers 2 inlets/outlets just for running to an HX for space heating . By only using a pump between an HX and the heater itself you can easily run your DHW and space heating applications . As a matter of fact they have already done this work for you by modifying the unit in the factory and calling it Versa Hydro . See their site and look at specs and watch the video with CEO and owner Dave Davis . You won't have to worry about all the nonsense if you do some minimum filtering or whatever amount of filtering / conditioning is required before Potable enters the tank . Not really much of a concern though with the materials these folks have used .

You didn't get what you didn't pay for and it will never be what you thought it would . Langans Plumbing & Heating LLC 732-751-1560 Serving most of New Jersey , Eastern Pa .Consultation , Design & Installation Rich McGrath 732-581-3833